The present invention relates to a semiconductor device.
To cope with an increase in the number of pins of a semiconductor chip, a bump pitch for flip chip bonding has lately become smaller. Because a related-art solder bump containing tin, and lead, as principal constituents, is turned bead-like in shape due to heat when the semiconductor chip is connected to a substrate, it has been difficult to realize miniaturization of a semiconductor device while maintaining a gap between the semiconductor chip, and a printed circuit board, and so forth. Meanwhile, it is recommended that a lead-free solder be substituted for a lead-base solder that was used as the constituent material of a bump in the past although the former is inferior to the latter in respect of melting point and ductility. Since the lead-free solder undergoes re-melting due to heat treatment in a back-end process such as a secondary bonding, and so forth, there exists a problem in that if a void exists in an under-fill material filling up the gap between the semiconductor chip, and the board, a molten solder will come into contact with a solder adjacent thereto, thereby causing a short circuit. In an attempt to solve those problems, development of a copper pillar technology for making use of copper for the constituent material of a bump has been underway. However, there has existed a problem that copper is harder as compared with the lead-base solder of the related art, and stress occurring to a bump due to a difference in coefficient of thermal expansion between the semiconductor chip, and the board will directly act on the semiconductor chip.
In Japanese Application Publication No. 2000-269371, there is described a configuration in which a projection is formed on a land which is a junction part of an external terminal of a semiconductor device, a protruding part of the projection is bonded with the external terminal, and further, an intercalated portion of a protection film made of a resin material is formed between the land and a semiconductor element. It is further described that the protection film is normally smaller in elastic coefficient than a land-forming material, and an external-terminal forming-material, and if the protection film is interposed between the land to which the external terminal is bonded, and a passivation film formed on the surface of the semiconductor element, this will enable deformation occurring to the external terminal owing to a difference in coefficient of linear expansion between the semiconductor device, and a printed circuit board to be mitigated by the agency of deformation occurring to the protection film. It is stated that by so doing, it is possible to reduce distortion occurring to respective junctions on the respective parts of the semiconductor device, and the printed circuit board.
In Japanese Application Publication No. 2000-243874, there is described a semiconductor device of the following configuration. An insulating coating is formed on the surface of a semiconductor chip, with an electrode terminal formed thereon, by exposing the electrode terminal of the semiconductor chip. Wiring patterns on one end side thereof, connected to the electrode terminal of the semiconductor chip, are formed on the insulating coating, and columnar electrodes are erected on the respective surfaces of lands formed on the other end side of the respective wiring patterns. There is formed a seal layer for sealing the surface of the semiconductor chip by exposing the top end face of each of the columnar electrodes. And the columnar electrode erected on the surface of the land is formed of a core made of a conductive metal, and a metal column formed by electroplating applied so as to embed the core. It is stated that by so doing, it is possible to increase the stress relaxation action of the columnar electrode while enhancing adhesion between the columnar electrode, and the land, and to shorten manufacturing time.
In Japanese Application Publication No. 2009-123862, there is described a semiconductor device including a semiconductor substrate with an electrode pad formed thereon, in conduction with a predetermined electronic circuit, a rewiring layer covering the electrode pad on the semiconductor substrate, and including a current-carrying part electrically connected to the electrode pad, a conductor post in a pillar-like shape, provided in a region on the rewiring layer, where the electrode pad is formed in the under-layer thereof, a part of the bottom surface of the conductor post, in contact with the rewiring layer, covering the electrode pad disposed in the under-layer, in whole, while being in conduction with the current-carrying part, and an external electrode formed in a predetermined region of the conductor post.
In Japanese Application Publication No. 2005-26679 as well, there is described a semiconductor device including a projection electrode. FIG. 12 shows a configuration of the semiconductor device in section. The semiconductor device includes a semiconductor substrate 101, an electrode pad 102, a passivation film 103 having a first opening for exposing a part of the surface of the electrode pad 102, an insulating film 104 having a second opening for exposing a part of the surface of the electrode pad 102, a projection electrode 106 having an outer edge, and a sealing resin 107. Wiring 105 is provided between the electrode pad 102, and the projection electrode 106, and an external terminal is provided on the surface of the projection electrode 106. The projection electrode 106 is disposed over the electrode pad 102 such that the outer edge is not superimposed on the second opening. In the case of a semiconductor device having a CSP structure, stress of a projection electrode portion thereof, converges on the edge thereof (a peripheral part, or an outer edge), however, by forming the opening of the insulating film 104 so as to be positioned directly underneath the projection electrode 106 and to be small in size such that the opening is included in the projection electrode in section, and by supporting the edge of the projection electrode, the stress converging thereon, with the insulating film 104 formed of polyimide and so forth, having relatively high elasticity, and a stress relaxation function, the passivation film 103, and the electrode pad 102, disposed underneath the insulating film 104, are protected from occurrence of cracking.